Caster wheels typically consist of a hub portion circumferentially encircled by a tire formed of rubber, polyurethane or other similar type material supported thereon. Casters are known having a pair of interconnected hub portions wherein each hub portion is provided with an annular rim or flange of a configuration adapted to oppose one another to form an annular recess or cavity for radially receiving the tire's inner radius portion. The tire's inner radius portion may be in the form of a pre-existing annular bead having a configuration complementary to that of the recess to form a tight fit therewith as shown in U.S. Pat. No. 3,895,668. Or, the inner radius may be deformed into a precise fit with the recess upon clamping the hub portions together as typified in U.S. Pat. No. 2,152,684.
While the aforementioned patents have achieved some degree of success a number of deficiencies in the constructions still exist. For instance, the construction in U.S. Pat. No. 2,152,684 does not permit the hub portions to be disassembled and reassembled to replace a worn tire. While U.S. Pat. No. 3,895,668 does permit the tire to be replaced, the construction utilizes a pneumatic tire and is of relatively low structural strength unsuitable for heavy duty applications.
Another deficiency with caster wheels of the aforedescribed type is that the recess does not permit the tire's inner radius portion to expand under load bearing conditions and, consequently, the outer radius portion of the tire compresses in an undesirable manner tending to cause the tire to wear unevenly and the caster wheel to roll inefficiently. Also, the known constructions do not includes tire support surfaces which support the entire length of the tire's side walls to form a solid radial column or incorporate projections to increase the frictional forces between the tire and the hub portions to prohibit rotation between the same.
It is an object of the invention to provide a caster wheel having a polyurethane tire having hub portions wherein the hub portions permit the tire to expand, or flow, under low bearing conditions to control the deformation of the tire.
Another object of the invention is to provide a caster wheel having a tire including an annular bead adjacent the inner diameter thereof radially supported within a dovetail cavity defined between hub portions wherein the cavity is of a larger axial dimension than the bead, thereby, permitting the bead and the adjacent portion of the tire to flow axially under load bearing conditions to together with hub portion sidewalls form a strong annular column having improved performance qualities.
A further object of the invention is to provide a caster wheel wherein one-piece hub portions are provided with support surfaces adapted to support substantially the entire length of the tire's side walls.
Yet a further object of the invention is to provide a caster wheel wherein the hub support surfaces are provided with a plurality of ribs to increase the friction between the tire and the hub portions and prohibit rotation between the same.
Still a further object of the invention is to provide a caster wheel which uses a simple construction, permits quick and easy replacement of the tire, and is useable for heavy duty applications.
Another object of the invention is to provide a caster wheel which is reliable in operation and is relatively inexpensive to manufacture.
In the practice of the invention a pair of complementary shaped one-piece hub portions each include a cylindrical segment having an axial passage extending therethrough between outer and inner ends and a radial flange. The hub portions, inner ends are adapted to be releasably clamped together by Allen bolts whereby the flanges oppose one another in space relation to radially support a tire. The tire is formed of a resilient material such as rubber or polyurethane and includes an annular bead adjacent the inner diameter thereof and a pair of spaced side walls radially extending from the bead.
The opposed flanges are of such configuration as to form an annular dove tail recess or cavity adapted to radially receive the tire's annular bead. The flanges also form a pair of outwardly divergently disposed tire support surfaces which radially extend from an opening adjacent the dove tail cavity to support substantially the entire length of the tire's side walls. A plurality of projections in the form of radially extending ridges or ribs are defined on the support surfaces to increase the friction between the tire and the hub portions to prohibit relative rotation therebetween.
The cavity is of a larger axial dimension than the axial dimension of the tire's bead which permits the inner radius portion of the tire to flow axially under load bearing conditions to accommodate for the compression forces imposed on the tire's outer radius portion whereby the tire's side walls are compressed radially inwardly into a frictional engagement with the support surfaces and the associated projections. This flowing controls the deformation of the tire, provides improved performance qualities in the caster wheel, and maintains the tire on the hub. Also, the life of the tire is prolonged as the tire tends to wear evenly.
Preferably, the hub portions are fabricated by a forging process to form a rugged construction suitable for heavy duty applications. Also, the caster wheel incorporates a simple construction which permits the tire to be quickly and conveniently replaced, when necessary, without the necessity of special tools or machines.